1. Field of the Invention
The present invention relates to tubular bodies made of metal and to a manufacturing method thereof. More specifically, the invention relates to a method of manufacturing side hole-bearing tubular bodies made of metal and having a small inside diameter which can be used in such applications as pins, syringe needles and connectors, and to the tubular bodies thereby manufactured.
2. Prior Art
Metal tubular bodies of small diameter, e.g., a bore of up to 2 mm, used in various medical applications such as pins, syringe needles and connectors, are sometimes provided with one or more side holes, depending on the particular application. For example, JP 2-65870 A describes an indwelling needle having a side hole formed in an area other than the needle point to increase the drug solution infusing effect into a blood vessel. In such side hole-bearing indwelling needles, as illustrated by the process disclosed in this prior-art publication, the side hole is typically created by a punching operation after the needle being produced has been formed into a tubular shape. However, indwelling needles, particularly those of a small bore, in which a side hole has been formed by such a process undergo deformation of the side hole-bearing surface when locally subjected to pressure at the side hole-forming site. The flattened area that forms as a result increases resistance to needle penetration during a medical procedure and raises the level of pain experienced at the time of puncture. Moreover, it has been impossible in prior-art processes to form side holes anywhere other than on the bevel portion of the needle without deforming the tubular shape. This has limited the position, shape and number of side holes that can be formed on such needles. Also, in the manufacture of indwelling needles by a conventional process, because the tubular body, once formed, is placed on a die and a side hole is punched therein, another drawback has been an increased number of manufacturing steps.